The present invention relates to the roof of an automobile such as a sedan, a limousine, a coupe, a station wagon, a van or a minibus with a top panel, a longitudinal beam along either side of the vehicle serving as the connecting element between the top panel and the side walls and/or the side-wall posts, and a roof rail protruding from either longitudinal side of the top panel of the vehicle for attaching top-carrier cross braces or the like.
A vehicle roof of the type mentioned above has been described for instance in DE 29 39 671 A1 or in DE 199 15 546 A1, and roof rack designs which are still commonly used have been covered in publications DE 35 24 558 A1 and, respectively, DE 35 29 449 A1.
The cost of producing a car top of the type mentioned above, or of producing and mounting a roof rack, is considerable, which is why this invention is essentially aimed at simplifying such production and substantially reducing its cost.
Accordingly, for a vehicle roof of the type referred to above, it is the objective of this invention to introduce a simplified car-top and roof-rail design which is substantially more cost-effective in comparison with prior art.
According to the invention, this objective is achieved by means of an integrated, single-unit longitudinal-beam and roof-rail combination module produced from the same material.
The solution according to this invention makes it possible to avoid having to separately produce and assemble the longitudinal car-top beams and the roof rail. Integrating the roof rail into a longitudinal beam eliminates a great many components that were needed in the past, such as support legs, adapters, mounting hardware, seals and gaskets etc., thus also obviating the need for producing and stocking these components.
The module per this invention, consisting of the longitudinal beam and the roof rail, may be designed in tubular box-frame fashion, curved to follow the contour of the vehicle roof.
In a preferred implementation of this invention, the roof rail part of the module features a continuous mushroom crown or at least on one side a longitudinal recess over which a fastening element of the roof-rack cross brace can be hooked. The mushroom crown, or the longitudinal recess provided at least on one side, gives the roof-rack of the finished vehicle optimal structural stability and, on the side facing and accessible to the observer, a particularly attractive appearance (the longitudinal beam of the car top is usually concealed by a metal trim).
The appearance of the roof-rail section of the module can be substantially enhanced if, according to a desirable variation of this invention, at least that roof-rail section is painted or anodized. The module may consist of steel or aluminum.
In a preferred implementation of this invention the module, composed of a possibly pre-bent tubular-frame, a longitudinal-beam and a roof-rail section, is produced by a forming process employing high internal pressure. In that process the tubular frame section, perhaps in the form of a contoured extrusion, is bent to follow the curvature of the object vehicle roof and is placed in the cavity of a tool that corresponds to the intended shape of the module, whereupon the forming tool is closed and a pressure medium is applied which causes internal pressure to build up inside the tubular frame section, stretching the tube to where it fully hugs the cavity wall of the forming tool. The preferred pressure medium is water, applied at a pressure of 2000 to 3000 bar. A forming process that employs high internal pressure is a simple and cost-effective way to produce a module encompassing a longitudinal-beam and a roof-rail section with a high degree of reproducible accuracy as well as product and product-surface quality. Tests have shown that cross-sectional modifications such as roof-rail end sections that slope off in height for instance relative to the longitudinal beam or which are tapered lengthwise, present no problems in production. Within broad limits it is possible, of course, to satisfy customer preferences relative to special cross-sectional configurations of the module both in terms of the longitudinal beam and of the roof rail.
The desire of car makers to increasingly use modular vehicle components is met by a design version of this invention in which the metal roof is inseparably connected to the modules that encompass a longitudinal-beam and a roof-rail section, constituting, together with the attached car ceiling, a complete prefabricated assembly unit. The car ceiling may include a fabric roof lining and/or interior soft trim, sun visors, inside rear view mirror, interior lighting, wiring, operating and instrument-panel elements, sliding or sun roof and its mounts and actuating elements, handles, and more. It will be necessary for such a prefabricated assembly unit to be so configured as to match the connecting points of the side walls or side-wall posts of the vehicle.